The invention relates generally to leak detectors for containers and deals more particularly with an apparatus for testing the sealability of the mouth of a container.
A wide variety of surface finish leak detectors were previously known such as those disclosed in U.S. Pat. Nos. 3,496,761 and 4,490,800. These detectors inspect the surface of a bottle mouth as the bottle is fed by a conveyor or auger screw to an inspection site located beneath the detector. The detector of U.S. Pat. No.3,496,761 includes a test fitting which is lowered into engagement with the mouth of the bottle at the inspection site and forms an air-tight seal if the bottle mouth is properly formed-smooth, flat and generally horizontal; otherwise, a leak results. The sealability of the bottle mouth by the test fitting mimics the sealability of the bottle mouth by a cap or other type of commercial seal.
In the various leak detectors previously known, air is injected into the bottle and pressure is sensed according to a variety of schemes. For example, in U.S. Pat. No. 3,496,761 a metered volume of air is injected into the container by a piston and cylinder assembly which forms a pump. At the conclusion of the discharge stroke of the piston and cylinder assembly, while the test fitting still closes the mouth of the container under test, the air pressure retained in the container is gauged to determine whether an excessive leakage takes place due to imperfections in the container mouth. While this system is effective in detecting flaws in the surface of a bottle mouth, it is limited in the rate at which it can inspect bottles. Also, the differences in pressure between good bottles and leakers varies with the amount of time available after the metered volume of air is injected in the bottle for the apparatus to subsequently measure the pressure in the bottle.
Accordingly, a general object of the present invention is to provide a detector to sense the sealability of a container mouth which detector is reliable and accurate and provides a high throughput.
A more specific object of the present invention is to provide a detector of the foregoing type which is reliable over a wide range of bottle throughputs.
Another specific object of the present invention is to provide a leak detector of the foregoing type which is reliable over a wide range of container capacities.
Another general object of the present invention is to provide a high speed detector to sense other types of leaks in containers.